Tropical Depression SEVEN-E

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TROPICAL DEPRESSION SEVEN-E DISCUSSION NUMBER 3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP072007
800 AM PDT SUN JUL 22 2007
FIRST-LIGHT VISIBLE IMAGERY SHOWS THAT THE BROAD CENTER OF TROPICAL
DEPRESSION SEVEN-E IS EAST OF THE PREVIOUS ADVISORY POSITION...
REQUIRING A RE-LOCATION. THE SYSTEM IS QUITE DISORGANIZED...WITH
THE CIRCULATION ELONGATED FROM NORTHEAST TO SOUTHWEST...AND
THE CONVECTION DISPLACED WEST OF THE CENTER BY 20-25 KT OF
EAST-NORTHEASTERLY VERTICAL WIND SHEAR. SATELLITE INTENSITY
ESTIMATES ARE 35 KT FROM BOTH TAFB AND SAB...BUT THESE MAY BE A BIT
GENEROUS. THE INITIAL INTENSITY IS SET TO A MORE CONSERVATIVE 30
KT.
THE INITIAL MOTION IS A RATHER UNCERTAIN 285/6. THE DEPRESSION IS
ON THE SOUTHWEST SIDE OF A RIDGE OVER MEXICO...WHICH SHOULD PERSIST
WITH SOME FLUCTUATIONS IN STRENGTH DURING THE NEXT 5 DAYS. THE
MODELS INDICATE THAT A MID-LEVEL SHORTWAVE TROUGH OVER NORTHEASTERN
MEXICO WILL MOVE SOUTHWESTWARD AROUND THE RIDGE AND INTERACT WITH
THE TROPICAL CYCLONE IN 36 HR OR SO. THIS EVOLUTION WOULD ALLOW
THE DEPRESSION TO MOVE WEST-NORTHWESTWARD FOR 24-36 HR FOLLOWED BY
A TURN TOWARD THE NORTHWEST. THE TRACK GUIDANCE GENERALLY AGREES
ON THIS...BUT THERE IS SOME SPREAD ON THE TIMING AND SHARPNESS OF
THE TURN. THE NOGAPS AND GFDN CALL FOR A MORE NORTHWARD TURN
CLOSER TO 110W...WHILE THE UKMET CALLS FOR A NORTHWESTWARD MOTION
STARTING AT 112W. THE NEW FORECAST TRACK IS SHIFTED SOMEWHAT THE
EAST OF THE PREVIOUS TRACK BASED ON THE INITIAL POSITION AND
MOTION...AND IS IN BEST AGREEMENT WITH THE CCON CONSENSUS MODEL.
IT SHOULD BE NOTED THAT THE SHORTWAVE TROUGH IS NOT READILY
APPARENT IN WATER VAPOR IMAGERY...AS IT MAY BE MASKED BY CLOUDS AND
MOISTURE AT HIGHER LEVELS.
LARGE-SCALE MODELS FORECAST THE CURRENT STRONG UPPER-LEVEL WINDS TO
CONTINUE FOR 36-48 HR...WHICH AT THE VERY LEAST SHOULD SLOW
DEVELOPMENT. THE MODELS FORECAST THE SHEAR TO DECREASE AFTER THAT
TIME. THE INTENSITY GUIDANCE FORECASTS SOME INTENSIFICATION
DESPITE THE SHEAR...WITH THE GFDL AND HWRF FORECAST A FASTER
DEVELOPMENT RATE AFTER THE SHEAR DECREASES. THE INTENSITY FORECAST
WILL CONTINUE THE TREND OF SLOW DEVELOPMENT FROM THE PREVIOUS
FORECAST...WITH A SLIGHTLY HIGHER PEAK INTENSITY AT 96 HR FOLLOWED
BY A WEAKENING TREND OVER COOLER SEA SURFACE TEMPERATURES AT 120
HR. AN ALTERNATE SCENARIO IS THAT LITTLE DEVELOPMENT MAY OCCUR
DURING THE FIRST 36-48 HR DUE TO THE SHEAR...FOLLOWED BY A MORE
NORMAL DEVELOPMENT RATE.
FORECAST POSITIONS AND MAX WINDS
INITIAL 22/1500Z 12.8N 105.9W 30 KT
12HR VT 23/0000Z 13.2N 107.2W 30 KT
24HR VT 23/1200Z 13.7N 108.6W 35 KT
36HR VT 24/0000Z 14.0N 109.7W 40 KT
48HR VT 24/1200Z 14.6N 110.5W 45 KT
72HR VT 25/1200Z 16.0N 111.5W 50 KT
96HR VT 26/1200Z 18.5N 113.0W 55 KT
120HR VT 27/1200Z 20.5N 115.5W 50 KT
$$
FORECASTER BEVEN
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